U.S. patent number 4,999,576 [Application Number 07/387,183] was granted by the patent office on 1991-03-12 for electrical-energy-supplying device having an extended storage life.
This patent grant is currently assigned to General Electric Company. Invention is credited to Lionel M. Levinson.
United States Patent |
4,999,576 |
Levinson |
March 12, 1991 |
Electrical-energy-supplying device having an extended storage
life
Abstract
An electrical-energy-supplying device having an extended storage
life includes a thermoelectric (TE) working module which has a hot
junction and a cold junction. A storage battery for supplying
electrical energy is thermally connected to the cold junction to
transfer heat from the battery to the hot junction of the TE module
when a voltage of proper polarity and magnitude is applied to the
TE module. A thermal sensor is thermally connected to the battery
and electrically connected to a cooling control circuit to cause
application of the voltage to the TE module when the battery
temperature exceeds a selected temperature level. The storage life
of the battery may be extended by maintaining the battery
temperature below the selected temperature level.
Inventors: |
Levinson; Lionel M.
(Schenectady, NY) |
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
23528834 |
Appl.
No.: |
07/387,183 |
Filed: |
July 31, 1989 |
Current U.S.
Class: |
324/142; 307/66;
429/62 |
Current CPC
Class: |
H01M
10/658 (20150401); H01M 10/63 (20150401); H01M
10/627 (20150401); G01R 31/382 (20190101); H01M
10/6572 (20150401); H01M 10/613 (20150401); H01L
35/00 (20130101); G01R 31/3648 (20130101); H01M
10/6554 (20150401); H01M 10/6551 (20150401); Y02E
60/10 (20130101); G01R 31/3832 (20190101) |
Current International
Class: |
H01L
35/00 (20060101); G01R 31/36 (20060101); H01M
10/50 (20060101); H01M 10/42 (20060101); G01R
021/06 (); H02J 009/00 (); H01M 010/50 () |
Field of
Search: |
;324/142,113,116,157
;307/66 ;365/229 ;429/62 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Karlsen; Ernest F.
Attorney, Agent or Firm: Snyder; Marvin Davis, Jr.; James
C.
Claims
What is claimed is:
1. A TOU watt-hour meter for measuring electrical energy usage from
a utility line, comprising:
metering means, having at least two terminals for connecting to the
utility line, for measuring electrical energy usage;
data means, coupled to said metering means, for recording
electrical energy usage and time of use information;
battery means for supplying electrical energy to said data means to
maintain accurate time information if the utility line energy is
interrupted;
a thermoelectric working module having a cold junction thermally
connected to said battery means, and a hot junction thermally
connected for heat dissipation away from said battery means;
and
cooling control means for causing said thermoelectric working
module to transfer heat energy away from said battery means when
said battery means exceeds a selected temperature.
2. The device of claim 1 further comprising an insulated enclosure
for housing said battery means with at least a portion of said cold
junction extending into said enclosure.
3. The device of claim 2 wherein said insulated enclosure has an
outer surface of heat and light reflective material.
4. The device of claim 2 wherein said insulated enclosure is
substantially filled with a foam-type insulation material.
5. The device of claim 2 wherein said insulated enclosure is
evacuated and includes a plurality of heat reflective shields
mounted within said enclosure.
6. The device of claim 1 further comprising heat sink means for
dissipating heat transferred to said hot junction.
7. The device of claim 6, wherein said heat sink means includes: a
thermally conductive plate; and a strap of thermally conductive
material thermally connected to transfer heat away from said
battery means to said plate for dissipation.
8. The device of claim 1, wherein said cooling control means
comprises:
switching means for connecting the voltage to said thermoelectric
module to cause cooling of said battery means; and
thermal sensor means, thermally connected to said battery means and
electrically connected to said switching means, for generating
electrical signals to cause said switching means to connect the
voltage to said thermoelectric module when said battery means
exceeds said selected temperature.
9. The device of claim 1, further comprising:
a transformer having a secondary winding and a primary winding for
connection to an AC line voltage; and
rectifier means, connected in an electrical path between said
transformer secondary winding and said thermoelectric working
module, for providing a DC voltage for application by said cooling
control means to said thermoelectric working module.
10. The device of claim 9, further comprising signal conditioning
means for reducing the harmonic ripple in a rectified AC signal
connected between said rectifier means and said thermoelectric
working module.
Description
BACKGROUND OF THE INVENTION
The present invention relates to battery backup power systems and,
more particularly, to a thermoelectric cooling device for extending
the life of a battery backup power system used for powering
electronic components when utility line power is interrupted or
unavailable.
Use of a battery or an electrolytic-type device to provide backup
power to electronic equipment during a power outage is known in the
art. One such application is with time of use (TOU) watt-hour
meters. TOU watt-hour meters permit electric utilities to apply
complex rate structures to their customers. TOU watt-hour meters
typically sample a customer's energy usage at selected times and
record the kilowatts used with the corresponding time of use; thus,
different billing rates can be applied for different times of the
day, days of the week and even during certain times of the year,
such as holidays and different seasons. These meters typically
utilize an application specific integrated circuit (ASIC),
microprocessor or the like for recording the kilowatts and the time
of use. The ASIC will also include a clock for measuring time and
maintaining calendar information. The ASIC and clock are powered by
the utility line power under normal operating conditions, but these
type meters also usually have a battery for backup ASIC power when
utility line power is interrupted. The battery will maintain
operation of the ASIC clock during power outages to prevent the
need for a maintenance visit by utility personnel to reset the
system clock and correct for the period of power outage after power
is restored.
A lithium-type battery may be used in TOU watt-hour meters to
maintain the ASIC clock during power outages, but these type
batteries have a limited shelf life and must be replaced about
every five years at a cost of about $10 per battery. Maintaining
reliable battery backup for TOU watt-hour meters is therefore a
considerable burden for utility companies when considering the
number of units in the field and the logistics and record-keeping
requirements. To meet the needs of most utility companies which use
TOU watt-hour meters, a desired backup battery power system will:
have a shelf life in excess of 20 years; and provide approximately
2-5 volts and 1-10 .mu.amps for more than about 30 days. Solid
state lithium iodine-type batteries, such as those used in heart
pacemakers and the like, typically have a life in excess of about
20 years when operated at body temperature, i.e., about 37.degree.
C. However, the life of these pacemaker-type batteries decreases
and the current and voltage levels are unreliable when the
batteries are stored at higher temperatures. TOU watt-hour meters
can be exposed to temperatures as high as about 85.degree. C. for
long periods in some climates; under such conditions, the capacity
of the battery can decrease by about 80 percent in five years.
It is accordingly a primary object of the present invention to
provide a novel cooling device for cooling a temperature-sensitive
component.
It is another object of the present invention to provide a novel
backup power supply device for a TOU watt-hour meter, which is not
subject to the foregoing disadvantages.
It is a further object of the present invention to provide a device
for cooling the backup battery for a TOU watt-hour meter to extend
the useful life of the backup battery.
These and other objects of the invention, together with the
features and advantages thereof, will become apparent from the
following detailed specification when read with the accompanying
drawings in which like reference numerals refer to like
elements
SUMMARY OF THE INVENTION
In accordance with the present invention, an
electrical-energy-supplying device having an extended storage life,
which may be used as a battery backup power system when utility
power is interrupted, includes a thermoelectric (TE) working module
which has a hot junction and a cold junction. A storage battery
means for supplying electrical energy is thermally connected to the
cold junction and a cooling control circuit is connected between
the TE working module and the utility power. The cooling control
circuit will apply a voltage of a selected magnitude and polarity
to the TE working module to cause heat transfer from the storage
battery means to the hot junction when the storage battery
temperature exceeds a selected level, preferably between about
20.degree. C.-25.degree. C. The battery and at least a top portion
of the cold junction in contact with the battery may be housed in
an insulated enclosure to improve cooling efficiency; the skin of
the enclosure may be fabricated from a heat and light
reflective-type material.
In accordance with an embodiment of the present invention, the
electrical-energy-supplying device may be mounted in the housing of
a TOU watt-hour meter to supply backup power to a data means, such
as an ASIC or the like, to cause the data means to maintain clock
and calendar information when utility power is interrupted.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a thermoelectric working
module.
FIG. 2 is a side elevation view of the electrical-energy-supplying
device in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The use of thermoelectric (TE) working modules for cooling (and
heating) is known in the art (Modern Thermo-electrics, D. M. Rowe
and C. M. Bhandari, Reston Publishing Co., 1983); a two-couple
single-stage TE module 10 is shown in FIG. 1. TE module 10 includes
a cold junction 12 and a hot junction 14 with multiple arms 16 of
thermoelectric material connected therebetween in thermal parallel.
The thermoelectric material may be bismuth telluride or an alloy of
bismuth, tellurium, selenium, antimony or similar type materials.
Arms 16 are alternately doped to have P or N type conductivity.
Arms 16 are electrically connected in series between electrical
input terminals 18a and 18b by connecting straps 20, which are
fabricated from a high electrically and thermally conductive
material such as copper, tungsten, nickel, stainless steel or the
like and arms 16 are thermally connected in parallel between cold
junction 12 and hot junction 14 by connection buses 22a and 22b,
which are fabricated of an electrical insulator with good thermal
conductivity such as alumina (Al.sub.2 O.sub.3) or the like. Pads
12' and 14', fabricated from solder-type material or the like, may
be respectively attached to buses 22a and 22b to facilitate
mechanical attachment of TE module 10 to a temperature-sensitive
component and/or a heat sink. In operation, a DC voltage source 24,
of proper polarity and magnitude, applied to input terminals 18a
and 18b will cause heat transfer from cold junction 12 through arms
16 to hot junction 14 to provide cooling at cold junction 12. Cold
junction 12 may be thermally connected to a temperature-sensitive
component (not shown) by pad 12' to cool the component. A reversal
of polarity will cause heat transfer in the alternate direction
(i.e. from hot junction 14 to cold junction 12) to provide
heating.
Referring to FIG. 2, a TOU watt-hour meter housing 26 is typically
mounted on an exterior wall 28 of a structure to which the utility
company is supplying electrical power. In accordance with the
present invention, an insulated enclosure 30 is mounted in meter
housing 26 at an appropriate location therein where enclosure 30
will not interfere with the operation of the metering equipment 31
(shown in block diagram form). Insulated enclosure 30 is preferably
constructed with at least an exterior surface 30a of a light and
heat reflective material so that sunlight will not appreciably heat
the components housed within. A thermoelectric (TE) working module
10 may be mounted within enclosure 30 and includes a cold junction
12, a hot junction 14, and a plurality of thermoelectric material
arms 16 thermally connected in parallel between the hot and cold
junctions. TE module 10 may also be mounted within meter housing
26, substantially external to enclosure 30, but with at least a
portion of cold junction 12 extending into enclosure 30 through an
opening 32 formed through the bottom of enclosure 30 (FIG. 2).
A copper or aluminum strap 33 or the like is preferably thermally
connected between hot junction 14 and a stationary metal plate 34
of the meter equipment, which acts as a heat sink to dissipate heat
transferred by strap 33 from hot junction 14 to plate 34. A heat
sink (not shown) may alternatively be integrally formed with hot
junction 14, which extends externally from insulated enclosure 30
and may also extend externally from meter housing 26 to permit heat
transferred to hot junction 14 to be dissipated into the
atmosphere.
A battery 36, such as a lithium type battery, "pacemaker-type"
battery or the like, is contained within insulated enclosure 30 and
is thermally connected to cold junction 12 extending through
enclosure opening 32. Battery 36 should typically have a casing of
heat conductive material to facilitate cooling of the battery as a
whole. Battery 36 includes battery terminals 36a and 36b for
electrically connecting battery 36 to a data means 38, such as an
application specific integrated circuit (ASIC), microprocessor or
the like, of the TOU watt-hour meter. Battery 36 will supply
electrical power to a clock, integrally formed with data means 38,
when utility line power is interrupted. Data means 38 is
electrically coupled to metering equipment 31 by a signal
transmission path 40 over which data means 38 receives electrical
usage information, which data means 38 stores with time of use
information. Metering equipment 31 has terminals 31a and 31b for
connecting the metering equipment to the utility power lines.
A transformer means 42 and a rectifier means 44 are mounted in
meter housing 26, preferably outside of insulated enclosure 30, to
provide a DC voltage to TE working module 10 when battery cooling
is required. The DC voltage required will be a function of the
capacity of TE module 10 and the cooling power desired. Transformer
means 42 has input terminals 42a and 42b for connecting the
transformer primary windings to the utility line power. The
secondary windings of transformer means 42 are connected to
rectifier means 44. Signal conditioning means 45, such as a
capacitive or inductive filter or the like, may be coupled to
rectifier means 44 for smoothing the DC signal resulting from the
rectified AC signal because the AC harmonics that appear in the DC
signal may have some effect on the cooling efficiency of the TE
working module. The reduction in cooling efficiency is proportional
to the harmonic ripple squared (R.sup.2); thus, a harmonic ripple
having amplitude that is about 20 percent of the magnitude of the
DC signal will cause a reduction in efficiency of about 4 percent.
Rectifier means 44 may be a regular rectifier, a Schottky
rectifier, or preferably a metal-oxide-semiconductor (MOS) device,
such as a power MOS field effect transistor (MOSFET) which has the
advantage of having a low forward on resistance so that very little
power is lost in the MOSFET when it is in a conductive state.
A cooling control circuit means 46 is also mounted in meter housing
26, preferably outside of insulated enclosure 30, and is connected
in an electrical path between the utility line power and TE working
module 10; cooling control circuit means 46 controls the
application of the DC voltage from signal conditioning means 45 to
TE module 10. Control circuit means 46 includes a thermal sensor
48, thermally connected to battery 36 for sensing the temperature
of battery 36. Cooling control circuit means 46 may include an
electrically controlled switch (not shown), such as a field effect
transistor or the like, and thermal sensor 48 may be a thermistor,
thermocouple or similar temperature-sensitive device. Thermal
sensor 48 is connected to cooling control circuit means 46 by
signal transmission path 50, which transfers electrical signals
from sensor 48 to cooling control circuit means 46. When sensor 48
detects a battery temperature in excess of a selected temperature
(preferably between about 20.degree.-25.degree. C.), cooling
control circuit means 46 will become conductive to apply DC voltage
of proper polarity and magnitude to TE module 10 to cause TE module
10 to transfer heat from battery 36 to hot junction 14 for
dissipation via strap 33 and heat sink plate 34. It should be noted
that while cooling control circuit 46 is shown to be electrically
connected to cold junction 12 by conductors 52a and 52b, cooling
control circuit 46 could equally be connected to apply a DC voltage
of opposite polarity to hot junction 14 to cause heat transfer from
battery 36 to hot junction 14. TE module 10 will only cool battery
36 when utility line power is uninterrupted but since power outages
are usually of a short duration, any short term heating of the
battery above the selected temperature is not expected to
appreciably shorten the battery's life. While FIG. 2 shows cooling
control circuit means 46 connected between rectifier means 44 and
TE module 10, cooling control circuit means 46 could equally be
designed for connection at any location between the utility line
power and TE module 10 and transformer means 42 and rectifier means
44 could be rearranged accordingly.
The interior volume 54 of insulated enclosure 30 may be packed with
a foam-type insulation, such as styrofoam or the like, to reduce
heating from external conditions, such as sunlight or the like, and
to improve cooling efficiency. A less economical but probably more
effective insulating technique is to evacuate enclosure 30 to form
a vacuum and mount reflective heat shields 56 within the enclosure.
Reflective heat shields 56 will retard the radiative transport of
heat and the vacuum will retard the convective and conductive
transport of heat to the battery/TE module combination. In this
environment, TE module 10 can be selected to have a cooling
capacity which will maintain the temperature of the battery at
about 20.degree. C. This battery temperature is expected to provide
a battery life in excess of about 20 years. Preferably, only the
components that need to be cooled are contained inside enclosure 30
to minimize the size of the enclosure and improve cooling
efficiency.
It will be readily understood by those skilled in the art that the
present invention is not limited to the specific embodiments
described and illustrated herein. Different embodiments and
adaptations besides those shown herein and described, as well as
many variations, modifications and equivalent arrangements will now
be apparent or will be reasonably suggested by the foregoing
specification and drawings, without departing from the substance or
scope of the invention. While the present invention has been
described herein in detail in relation to its preferred
embodiments, it is to be understood that this disclosure is only
illustrative and exemplary of the present invention and is made
merely for purposes of providing a full and enabling disclosure of
the invention. Accordingly, it is intended that the invention be
limited only by the spirit and scope of the claims appended
hereto.
* * * * *